pkg/config: Set defaults for existing pprof configs again

[metalmatze]

Somehow this code was removed. Because of that, if enabled or path aren't specified in the config they simply were left untouched and therefore weren't enabled or with the wrong path, / instead of /debug/pprof/...

What the in-memory config looked like after unmarshalling before this fix:

What the in-memory config looks like after unmarshalling with this fix:

closes #4883

[alwaysmeticulous]

✅ Meticulous spotted zero visual differences across 609 screens tested: view results.

_{Expected differences? Click here. Last updated for commit 492376c. This comment will update as new commits are pushed.}

[brancz]

@alperkokmen you might want to test whether everything still works as expected after this merges. I suspect it should be fine, but just wanted to call it out since #4623 originally removed these defaults.

[metalmatze]

Yes, I did test them locally with our scraper configuration. This is exactly what broke it, and now it's working again. I'll do some more testing once we have a container image.

[metalmatze]

Before this section was removed the code was like this.

Suggested change

	for pt := range unmarshalled.ProfilingConfig.PprofConfig {
	for pt := range defaults.ProfilingConfig.PprofConfig {
	// nothing set yet so simply use the default
	if unmarshalled.ProfilingConfig.PprofConfig[pt] == nil {
	unmarshalled.ProfilingConfig.PprofConfig[pt] = pc
	continue
	}

Maybe we want that again, but that means that we always add all defaults and then rather disable the ones we don't want?! I suppose that was the original behavior, though.